Boeing must perform more work on its proposed fix to 737 MAX aircraft before it can be submitted for review, US officials said on Monday, suggesting the planes could stay grounded a while longer. Additional work is needed “to ensure that Boeing has identified and appropriately addressed all pertinent issues,” a Federal Aviation Administration spokesman said in a statement.
The FAA will not approve the software for installation until the agency is satisfied with the submission, he added.
The FAA statement is the bureaucratic equivalent of a stop sign after Boeing officials touted their proposed remedy last week during a media tour at the company's manufacturing plant in Seattle, Washington.
Boeing's 737 MAX planes were grounded globally last month following the second of two deadly crashes to occur in less than five months.
Scrutiny has centered on an anti-stall system developed specifically for the planes that has given pilots problems.
A preliminary report into the second calamity - the Mar 10 crash of a Boeing 737 MAX 8 that killed 157 people - will likely be issued this week, the Ethiopian government said on Monday.
Boeing last week gathered hundreds of pilots and reporters at its Renton, Washington manufacturing site for a presentation on proposed changes to the Maneuvering Characteristics Augmentation System, which is believed to have been a key factor in the Ethiopian crash and in an October crash of a Lion Air in Indonesia that killed 189 people.
Among the changes, the MCAS will no longer repeatedly make corrections when the pilot tries to regain control, and will automatically disconnect in the event of disagreements between the two angle of attack, or AOA sensors, the company said last week.
Boeing is anxious to win approval for a proposed remedy that could get the planes back in the air. But the FAA, which faced harsh questioning last week at a congressional hearing regarding its oversight of Boeing, said it expected Boeing to submit the proposed fix over the coming weeks after it undertakes additional work.
After that, the proposal will be submitted to a rigorous safety review, the FAA spokesman said.
A Boeing spokesman said on Monday the company was continuing to work with regulators to address concerns.